Updated documentations

Author: ijlee2

CONTRIBUTING.md

@@ -145,7 +145,7 @@ The following reference-style patterns should not be used:
 
 ## Spellchecking/linting
 
-The guides are spellchecked and linted for markdown consistency. You can test your contributions by running `npm run lint:md`. Linting and spellchecking must pass or they will fail in Travis-CI. 
+The guides are spellchecked and linted for markdown consistency. You can test your contributions by running `npm run lint:md`. Linting and spellchecking must pass or they will fail in CI (continuous integration). 
 
 Markdown issues that will generate errors include:
 - Lists and text must be left justified, otherwise the linter will generate indentation errors

MAINTAINERS.md

@@ -4,7 +4,7 @@ This document contains instructions and guidelines for maintainer tasks, like pu
 
 ## Continuous deployment
 
-Whenever a PR is merged into `master`, Travis will automatically run the scripts that build the app and upload the results to Netlify. Netlify will then deploy the site. We currently allow only one Travis job at a time so that concurrent deploy commands do not cause a conflict.
+Netlify will deploy the site when a PR is successfully merged into `master`.
 
 ## Deploying a new version
 

README.md

@@ -1,4 +1,4 @@
-[![Build Status](https://travis-ci.org/ember-learn/guides-source.svg?branch=master)](https://travis-ci.org/ember-learn/guides-source)
+[![This project uses GitHub Actions for continuous integration.](https://github.com/ember-learn/guides-source/workflows/CI/badge.svg)](https://github.com/ember-learn/guides-source/actions?query=workflow%3ACI)
 [![This project is using Percy.io for visual regression testing.](https://percy.io/static/images/percy-badge.svg)](https://percy.io/Ember/guides-app)
 
 # Ember Guides Source
@@ -69,7 +69,7 @@ The guides are spellchecked and linted for Markdown consistency. You can check y
 npm run lint:md
 ```
 
-Linting and spellchecking must pass or they will fail in Travis-CI. See [CONTRIBUTING.md](CONTRIBUTING.md) for more information on linting and spellchecking.
+Linting and spellchecking must pass or they will fail in CI (continuous integration). See [CONTRIBUTING.md](CONTRIBUTING.md) for more information on linting and spellchecking.
 
 ### Internal and external links